Array substrate for reflective and transflective liquid crystal display devices and manufacturing method for the same

ABSTRACT

An array substrate for a reflective liquid crystal display device, including a gate line and a data line defining a pixel region by crossing each other; a switching element at a crossing portion of the gate line and the data line; a first passivation layer covering the switching element and the data line; and formed of an inorganic insulating material; a reflective electrode on the first passivation layer, and connected to the switching element; and a second passivation layer on the reflective electrode. The second passivation layer being formed of an organic insulating material.

This application is a Divisional of co-pending application Ser. No.10/028,759, filed on Dec. 28, 2001, and for which priority is claimedunder 35 U.S.C. § 120; and this application claims priority ofApplication No. 2001-7097 and 2001-30699 filed in Korea on Feb. 13, 2001and Jun. 1, 2001, under 35 U.S.C. § 119; the entire contents of all arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to liquid crystal display devices, andmore particularly, to an array substrate for reflective andtransflective liquid crystal display devices.

2. Description of the Background Art

Generally, a reflective liquid crystal display device does not need toequip an additional light source such as a back light because it cansubstitute an external light source for the back light. A transflectiveliquid crystal display device has both properties of the reflectiveliquid crystal display device and a transmissive liquid crystal displaydevice. Because the transflective liquid crystal display device utilizesboth of the back light and the external light source, it can save powerconsumption.

FIG. 1 illustrates a liquid crystal panel for a conventionaltransflective liquid crystal display device. The conventionaltransflective liquid crystal display device 11 has an upper substrate 15that includes a color filter 18 a transparent common electrode 13 and alower substrate 21 that includes a pixel region “P”, a pixel electrode19, thin film transistor and an array of gate lines 25 and data lines27. The color filter 18 includes a black matrix 16 and sub-color filtersR, G and B. The pixel electrode 19 has a transmission portion “A” and areflection portion “C”. Liquid crystal 23 is interposed between theupper substrate 15 and the lower substrate 21. The lower substrate 21 isalso referred to as an array substrate with thin film transistors “T”,switching elements, arranged in a matrix on the array substrate 21. Aplurality of horizontal gate lines 25 and a plurality of vertical datalines 27 cross each other defining the pixel region “P”. If thetransparent pixel electrode 19 and the transmission portion “A” areomitted from the transflective liquid crystal display device, it becomesa reflective liquid crystal display device.

FIG. 2 is a plan view illustrating a partial array substrate for aconventional reflective liquid crystal display device. As shown in thefigure, a plurality of gate lines 25 and a plurality of data lines 27cross each other defining a pixel region “P”. A thin film transistor “T”is formed at a crossing portion of the gate line 25 and the data line27. The thin film transistor “T” usually includes a gate electrode 32, asource electrode 33, a drain electrode 35 and an active layer 34. Apixel electrode 19 is formed in the pixel region “P” and the thin filmtransistor “T” connected to the drain electrode 35 drives the liquidcrystal 23 of FIG. 1. A reflective electrode, which is formed of opaqueconductive metal having a high reflexibility, is substituted for thepixel electrode 19 in the reflective liquid crystal display device. Theopaque conductive metal is selected from a group consisting of aluminum(Al) and aluminum alloys (AlNd, for example), for example.

Because the reflective liquid crystal display device uses an externallight source, incident light from the external light source passesthrough the upper substrate (not shown) and is then reflected at thereflective electrode 10 on the array substrate 21. The reflected lightsubsequently passes through the liquid crystal and thereby polarizationproperties of the light are changed according to birefringenceproperties of the liquid crystal. Color images can be displayed when thelight passing through the liquid crystal colors the color filter.

FIG. 3 is a cross-sectional view taken along III-III of FIG. 2 accordingto the conventional art. As shown in the figure, a gate electrode 32 anda gate line 25 of FIG. 2 are formed on a substrate 21. A gate insulatinglayer 41 is formed on the substrate 21 and on the gate electrode 32. Anactive layer 34 is formed on the gate insulating layer 41 and partiallyoverlapped with a source electrode 33 and a drain electrode 35. Thesource electrode 33, the drain electrode 35 and the data line 27 areformed on the active layer 34. A thin film transistor includes the gateelectrode 32, the source electrode 33, the drain electrode 35 and theactive layer 34. A passivation layer 43 made of insulating material isformed on the thin film transistor. The passivation layer 43 issubsequently patterned to form a drain contact hole 45 exposing a partof the drain electrode 35. A reflective electrode 19 contacts the drainelectrode 35 through the drain contact hole 45. The material for thereflective electrode 19 is selected from a group including aluminum (Al)and aluminum alloy (AlNd, for example), etc.

FIG. 5 is a cross-sectional view taken along line V-V of FIG. 4according to the conventional art. A thin film transistor “T” includinga gate electrode 32, a source electrode 33, a drain electrode 35 and anactive layer 34 is formed and a first passivation layer 43 is formed onthe thin film transistor “T”. The first passivation layer 43 is formedby depositing a transparent organic insulating material such asbenzocyclobutene (BCB) and acrylic resin. A drain contact hole 45 thatexposes a part of the drain electrode 35 is formed and a etching hole 53is formed by etching the first passivation layer 43 corresponding to thetransmission hole 53 in the pixel region “P”. A reflective electrode 19a that contacts the drain electrode 35 through the drain contact hole 45is formed in the pixel region “P”. The reflective electrode 19 a isformed of aluminum (Al) and aluminum alloys (AiNd, for example), etc. Asecond passivation layer 47 is formed on the reflective electrode 19 aand patterned to expose the reflective electrode 19 a corresponding tothe drain contact hole 45. The second passivation layer 47 is formed ofinsulating material such as silicon oxide (SiO₂) or silicon nitride(SiN_(X)), for example. A transparent pixel electrode 19 b that contactsthe exposed reflective electrode 19 a through the patterned secondpassivation layer 47 is formed on the second passivation layer 47.

Several masks for patterning array elements of the array substrate areused in the manufacturing of the conventional reflective andtransflective liquid crystal display device. An align key for accuratealigning of the mask and the substrate is formed on the corner of thesubstrate simultaneously with the gate line or the data line formingprocess. The shape of the align key has unevenness. Accordingly, adetector aligns the mask and the substrate by irradiating light onto theuneven surface of the align key and sensing the light reflected from thesurface of the align key.

FIG. 6 is a plan view illustrating a partial array substrate having acoplanar type polysilicon thin film transistor for a conventionaltransflective liquid crystal display device. A gate line 71 and a dataline 84 cross each other defining a pixel region “P” and a thin filmtransistor “T” is formed at a crossing portion of the gate line 71 andthe data line 84. The thin film transistor “T” is a polysilicon thinfilm transistor that includes a polysilicon active layer and has acoplanar structure in which a gate electrode 70 is formed under a sourceelectrode 80 and a drain electrode 82. A gate pad 74 and a data pad 86,which receive an external signal, are formed respectively at one end ofthe gate line 71 and the data line 84. The gate pad 74 and the data pad86 respectively contact a gate pad terminal 94 and a data pad terminal96 that are formed of transparent conductive material. The thin filmtransistor “T” includes the gate electrode 70, the source electrode 80,the drain electrode 82 and an active layer 66. The active layer 66 hasan active layer expanded portion 67 in the pixel region “P”. A storageline 72 is formed parallel to the gate line 71 with a same material asthat of the gate line 71 and has a storage line expanded potion 73 inthe pixel region “P”. The pixel electrode 63 contacts the drainelectrode 82. A storage capacitor portion “C” and a reflection portion“E” are formed in the pixel region “P”. A reflector 102 is formed on thestorage capacitor portion “C”. The rest potion of the pixel region “P”except the reflector 102 is a transmission portion “F”.

FIGS. 7A to 7F are cross-sectional views taken along IV-IV, V-V, VI-VIof FIG. 6 illustrating a fabricating sequence of an array substrateaccording to the related art. In FIG. 7A, a first insulating layer 62 isformed on a substrate 60 by depositing inorganic insulating materialsuch as silicon oxide (SiO₂) or silicon nitride (SiN_(X)) and anamorphous silicon layer 64 is formed on the first insulating layer bydepositing amorphous silicon (a-Si:H). The first insulating layer 62,referred to as a buffer layer, is for preventing an expansion ofalkaline substances from the substrate 60. The amorphous silicon layer64 is crystallized into polysilicon by introducing a solid phasecrystallization (SPC) method, a metal induced crystallization (MIC)method, a laser annealing method and a field effect metal inducedcrystallization (FEMIC) method.

In FIG. 7B, a semi-conductor layer 66 is formed by patterning thecrystallized layer and a gate insulating layer 68, a second insulatinglayer, is formed on the semi-conductor layer 66. A conductive metallayer is subsequently formed on the gate insulating layer 68. A gateelectrode 70 and a gate line 71 of FIG. 6 are formed by patterning thedeposited conductive metal layer. The semi-conductor layer 66 has asemi-conductor layer expanded portion 67 in the pixel region “P”. Thegate pad 74 is formed at one end of the gate line 71. The storage line72 is simultaneously formed parallel to the gate line 71 and the storageline 72 has the storage line expanded portion 73 on the pixel region“P”.

The semi-conductor layer 66 can be divided into two regions, one is afirst active region “A” and the other is a second active region “B”. Thefirst active region “A” is a pure silicon region and the second activeregion “B” is an impure silicon region. The second active regions “B”are positioned at both sides of the first active region “A”. The gateinsulating layer 68 and the gate electrode 70 are formed on the firstactive region “A”. After forming of the gate electrode 70, ion doping isperformed onto the second active region “B” to form a resistant contactlayer. The gate electrode 70 serves as an ion stopper that preventsdopants from penetrating into the first active region “A”. After the iondoping is finished, the semi-conductor layer 66, the polysilicon island,implements a specific electric characteristic, which varies with typesof the dopants. If the dopant is, for example, B₂H₆ that includes aGroup III element, a doped portion of the polysilicon island 66 becomesa p-type semiconductor. Whereas, if the dopant is PH₃ that includes aGroup VI element, the doped portion of the polysilicon island 66 becomesan n-type semiconductor. A proper dopant should be selected to satisfythe use of a device. After the dopant is applied onto the polysiliconisland 66, the dopant is activated.

In FIG. 7C, a third insulating layer 76, i.e, an interlayer insulator,is formed over the whole area of the substrate 60 and is patterned toform a source contact hole 78 a and a drain contact hole 78 b. A sourceelectrode 80 and a drain electrode 82, which contact the second activeregion “B” through the source contact hole 78 a and the drain contacthole 78 b, respectively, are formed by depositing and then patterningconductive metals such as aluminum (Al), aluminum alloys, tungsten (W),copper (Cu), chromium (Cr) and molybdenum (Mo), etc. A data line 84 thatcontacts the source electrode 80 is simultaneously formed and a data pad86 is formed at one end of the data line 84. The polysilicon thin filmtransistor “T” is formed through the above processes.

In FIG. 7D, a fourth insulating layer 88 is formed on the whole area ofthe substrate 60 and then the thin film transistor undergoes ahydrogenation process. The hydrogenation process is for removing defectsthat occurred on the surface of the active layer 66. A fifth insulatinglayer 90 is formed on the fourth insulating layer 88 using transparentorganic insulating material such as benzocyclobutene (BCB) or acrylicresin. A first drain contact hole 92 exposing the drain electrode 82, agate pad contact hole 91 exposing the gate pad 74 and a data pad contacthole 95 exposing the data pad 86 are formed by patterning simultaneouslythe laminated layers.

In FIG. 7E, a pixel electrode 93 that contacts the exposed drainelectrode 82 and is extended to the pixel region, a gate pad terminal 94that contacts the exposed gate pad and a data pad terminal 96 thatcontacts the exposed data pad are formed on the fifth insulating layer90 using transparent conductive material such as indium tin oxide (ITO)or indium zinc oxide (IZO), for example.

In FIG. 7F, a sixth insulating layer 98 is formed on the whole area ofthe substrate 60 using silicon oxide (SiO₂) or silicon nitride(SiN_(X)), for example. A second drain contact hole 100 that exposes thepixel electrode 93 contacting the drain electrode 82 is formed bypatterning the sixth insulating layer 98. A reflective electrode 102,which contacts the exposed pixel electrode 93, is formed on the sixthinsulating layer 98 using conductive metal such as aluminum (Al) oraluminum alloys, for example. A first etching hole 104 that exposes thegate pad terminal 94 and a second etching hole 106 that exposes the datapad terminal 96 are formed by patterning the sixth insulating layer 98.The reason for exposing the gate pad terminal 94 and the data padterminal 96 in the last process is to prevent the pixel electrode 93 andthe reflective electrode 102 from being etched together in etchingsolution during an etching process for the reflective electrode 102.

Conventional reflective or transflective liquid crystal display deviceshave some problems described as follows. First, because a reflectiveelectrode is formed on an organic insulating layer such asbenzocyclobutene (BCB) and the contact property of the reflectiveelectrode and the benzocyclobutene (BCB) layer is not good, thereflective electrode may not be stably deposited on the organicinsulating layer. This lacks of stability lowers electric properties ofa liquid crystal panel. Second, when a sputtering process is used forforming the reflective electrode on the benzocyclobutene (BCB),accelerated electrons collide into the surface of the benzocyclobutene(BCB) and separate the benzocyclobutene (BCB) particles from thesurface, which produces benzocyclobutene (BCB) particles in a depositionchamber. The benzocyclobutene (BCB) particles in the deposition chambercontaminate the deposition chamber. Lastly, an align key may not bedetected by a detecting apparatus if the benzocyclobutene (BCB) isdeposited on the substrate and covers the align key. Accordingly,alignment error of a mask and the substrate may be occurred during alight exposing process for patterning the reflective electrode.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an array substrate forreflective and transflective liquid crystal display devices and amanufacturing method of the array substrate for reflective andtransflective liquid crystal display devices that substantially obviatesone or more of problems due to limitations and disadvantages of therelated art.

An object of the present invention is to provide an array substrate fora reflective liquid crystal display device, wherein a reflectiveelectrode is not formed on organic insulating material such asbenzocyclobutene (BCB), but formed on inorganic insulating material suchas silicon nitride (SiN_(X)) to improve contact property of thereflective electrode and to prevent a deposition chamber from beingcontaminated with particles of the organic insulating material.

Another object of the present invention is to provide a manufacturingmethod of an array substrate for a reflective liquid crystal displaydevice.

Another object of the present invention is to provide an array substratefor a transflective liquid crystal display device, wherein a reflectiveelectrode is not formed on organic insulating material such asbenzocyclobutene (BCB), but formed on inorganic insulating material suchas silicon nitride (SiN_(X)) to improve contact property of thereflective electrode and to prevent a deposition chamber from beingcontaminated with particles of the organic insulating material.

Another object of the present invention is to provide a manufacturingmethod of an array substrate for a transflective liquid crystal displaydevice.

Another object of the present invention is to provide an array substratefor a transflective liquid crystal display device having a barrier layerbetween an organic insulating layer and a reflector to improve contactproperty of the reflective electrode and to prevent a deposition chamberfrom being contaminated with particles of the organic insulatingmaterial.

Another object of the present invention is to provide a manufacturingmethod of an array substrate for a transflective liquid crystal displaydevice having a barrier layer between an organic insulating layer and areflector.

To achieve these and other advantages, one embodiment of the presentinvention, an array substrate for a reflective liquid crystal displaydevice includes a gate line and a data line defining a pixel region bycrossing each other, a switching element at a crossing portion of thegate line and the data line, a first passivation layer covering theswitching element and the data line, the first passivation layer beingformed of inorganic insulating material, a reflective electrode on thefirst passivation layer, the reflective electrode being connected to theswitching element, and a second passivation layer on the reflectiveelectrode, the second passivation layer being formed of organicinsulating material. The reflective electrode is formed of conductivemetal material such as aluminum (Al) or aluminum alloys, for example.The switching element is a thin film transistor including a gateelectrode, a source electrode, a drain electrode and an active layer.The first passivation layer is desirably formed of silicon nitride(SiN_(X)). The second passivation layer is formed of organic insulatingmaterial such as benzocyclobutene (BCB) or acrylic resin, for example.

In another aspect, a preferred embodiment of a manufacturing method ofan array substrate for a reflective liquid crystal display deviceincludes the steps of forming a gate line and a data line that define apixel region by crossing each other; forming a switching element at acrossing portion of the gate line and the data line; forming a firstpassivation layer covering the switching element and the data line; thefirst passivation layer being formed of inorganic insulating material;forming a reflective electrode on the first passivation layer, thereflective electrode being connected to the switching element; and,forming a second passivation layer on the reflective electrode. Thesecond passivation layer being formed of organic insulating material.

The reflective electrode may be formed of conductive metal material suchas aluminum (Al) or aluminum alloys, for example. The switching elementis a thin film transistor including a gate electrode, a sourceelectrode, a drain electrode and an active layer. The first passivationlayer is preferably formed of silicon nitride (SiN_(X)). The secondpassivation layer is formed of organic insulating material such asbenzocyclobutene (BCB) or acrylic resin, for example.

In another embodiment, an array substrate for a transflective liquidcrystal display device includes a gate line and a data line defining apixel region by crossing each other; a switching element at a crossingportion of the gate line and the data line; a first passivation layercovering the switching element and the data line and being formed ofinorganic insulating material; a reflective electrode on the firstpassivation layer, connected to the switching element and including atransmission hole; a second passivation layer on the reflectiveelectrode, formed of organic insulating material and patterned to exposea part of the switching element; and a transparent pixel electrode onthe second passivation layer, formed in the pixel region and contactingthe exposed part of the switching element.

The reflective electrode is formed of conductive metal material such asaluminum (Al) or aluminum alloys, for example. The switching element isa thin film transistor including a gate electrode, a source electrode, adrain electrode and an active layer. The first passivation layer isdesirably formed of silicon nitride (SiN_(X)). The second passivationlayer is formed of organic insulating material such as benzocyclobutene(BCB) or acrylic resin, for example.

In another embodiment, a manufacturing method of an array substrate fora transflective liquid crystal display device includes the steps offorming a gate line and a data line defining a pixel region by crossingeach other; forming a switching element at a crossing portion of thegate line and the data line; forming a first passivation layer coveringthe switching element and the data line, the first passivation layerbeing formed of inorganic insulating material; forming a reflectiveelectrode on the first passivation layer, the reflective electrode beingconnected to the switching element and including a transmission hole;forming a second passivation layer on the reflective electrode, thesecond passivation layer being formed of organic insulating material andpatterned to expose a part of the switching element; and forming atransparent pixel electrode on the second passivation layer. The pixelelectrode being formed in the pixel region and contacting the exposedpart of the switching element. The reflective electrode is formed ofconductive metal material such as aluminum (Al) or aluminum alloys, forexample. The switching element is a thin film transistor including agate electrode, a source electrode, a drain electrode and an activelayer. The first passivation layer is desirably formed of siliconnitride (SiN_(X)). The second passivation layer is formed of organicinsulating material such as benzocyclobutene (BCB) or acrylic resin, forexample.

In another embodiment, an array substrate for a transflective liquidcrystal display device includes a thin film transistor including anactive layer a gate electrode and source and drain electrodes, beingformed on a substrate in sequence; a gate line including a gate pad atone end of it, the gate line being connected to the gate electrode; astorage line being formed parallel to the gate line and being spacedapart from the gate line; a data line defining a pixel region bycrossing the gate line, including a data pad at one end of it and beingconnected to the source electrode; an organic insulating layer over thethin film transistor and the data line; a barrier layer on the organicinsulating layer and formed of inorganic insulating material; areflector on the barrier layer, and a transparent pixel electrode on aninorganic insulating layer. The pixel electrode contacting the drainelectrode, and the inorganic insulating layer being formed between thereflector and the pixel electrode. The array substrate for atransflective liquid crystal display device may further include a bufferlayer beneath the active layer using inorganic insulating material suchas silicon oxide (SiO₂) or silicon nitride (SiN_(X)), for example. Theactive layer is formed of polysilicon. The storage line is desirablyformed with a same material as that of the gate line on a same layer asthat of the gate line. The reflector is formed of conductive metalmaterial such as aluminum (Al) or aluminum alloys, for example. Thepixel electrode is formed of transparent conductive material such asindium tin oxide (ITO) or indium zinc oxide (IZO), for example. Thereflector may desirably be extended to the data line and simultaneouslycover the thin film transistor. The reflector may be partiallyoverlapped with the gate line and the gate line. The barrier layer isformed using inorganic insulating material such as silicon oxide (SiO₂)or silicon nitride (SiN_(X)), for example. The array substrate furthermay include an insulating layer beneath the organic insulating layer toperform a hydrogenation process of the thin film transistor. The barrierlayer is desirably formed of silicon nitride (SiN_(X)).

In another embodiment, a manufacturing method of an array substrate fora transflective liquid crystal display device includes the steps offorming a thin film transistor including an active layer, a firstinsulating layer, a gate electrode, a second insulating layer beingformed on a substrate in sequence; forming a gate line and a storageline such that, the gate line includes a gate pad at one end of it andbeing connected to the gate electrode; and the storage line is formedparallel to the gate line and spaced apart from the gate line; forming adata line defining a pixel region by crossing the gate line including adata pad at one end of it and being connected to the source electrode,forming a third insulating layer over the thin film transistor and thedata line, the third insulating layer being formed of transparentorganic insulating material; forming a fourth insulating layer on thethird insulating layer, the third insulating layer being a barrier layerand being formed of inorganic insulating material; forming a reflectoron the barrier layer; forming a drain contact hole over the drainelectrode by depositing and patterning a fifth insulating layer on thereflector; and forming a transparent pixel electrode on an inorganicinsulating layer, the pixel electrode contacting the drain electrode.The inorganic insulating layer being formed between the reflector andthe pixel electrode. The array substrate for a transflective liquidcrystal display device may further include a buffer layer beneath theactive layer using inorganic insulating material such as silicon oxide(SiO₂) or silicon nitride (SiN_(X)), for example. The active layer isformed of polysilicon. The storage line is desirably formed with a samematerial as that of the gate line on a same layer as that of the gateline. The reflector is formed of conductive metal material such asaluminum (Al) or aluminum alloys, for example. The pixel electrode isformed of transparent conductive material such as indium tin oxide (ITO)or indium zinc oxide (IZO). The reflector may desirably be extended tothe data line and cover the thin film transistor. The reflector may bepartially overlapped with the gate line and the gate line. The barrierlayer is formed using inorganic insulating material such as siliconoxide (SiO₂) or silicon nitride (SiN_(X)), for example. Themanufacturing method of the array substrate according to the presentinvention further includes forming an insulating layer beneath theorganic insulating layer to perform a hydrogenation process of the thinfilm transistor. The barrier layer is desirably formed of siliconnitride (SiN_(X)).

These and other objects of the present application will become morereadily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention and wherein:

FIG. 1 is an exploded perspective view illustrating a liquid crystalpanel for a conventional transflective liquid crystal display device;

FIG. 2 is a plan view illustrating a partial array substrate for aconventional reflective liquid crystal display device;

FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2according to the conventional art;

FIG. 4 is a plan view illustrating a partial array substrate having aninverted stagger type thin film transistor for a conventionaltransflective liquid crystal display device;

FIG. 5 is a cross-sectional view taken along line V-V of FIG. 4according to the conventional art;

FIG. 6 is a plan view illustrating a partial array substrate having acoplanar type polysilicon thin film transistor for a conventionaltransflective liquid crystal display device;

FIGS. 7A to 7F are cross-sectional views taken along lines IV-IV, V-V,VI-VI of FIG. 6 illustrating a fabricating sequence of an arraysubstrate according to the conventional art;

FIG. 8 is a plan view illustrating a partial array substrate for areflective liquid crystal display device according to a first embodimentof the present invention;

FIGS. 9A to 9C are cross-sectional views taken along III-III of FIG. 8illustrating a method of manufacturing an array substrate according tothe first embodiment of the present invention;

FIG. 10 is a plan view illustrating a partial array substrate having aninverted stagger type thin film transistor for a transflective liquidcrystal display device according to a second embodiment of the presentinvention;

FIGS. 11A to 11E are cross-sectional views taken along line V-V of FIG.10 illustrating a fabricating sequence of an array substrate accordingto the second embodiment of the present invention;

FIG. 12 is a plan view illustrating a partial array substrate having acoplanar type polysilicon thin film transistor for a transflectiveliquid crystal display device according to a third embodiment of thepresent invention; and

FIGS. 13A to 13F are cross-sectional views taken along lines IV-IV, V-V,VI-VI of FIG. 12 illustrating a fabricating sequence of an arraysubstrate according to the third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiment of thepresent invention, which is illustrated in the accompanying drawings.

A first embodiment of the present invention will be describedhereinafter with reference to FIG. 8 and FIGS. 9A to 9C. FIG. 8 is aplan view illustrating a partial array substrate for a reflective liquidcrystal display device according to the first embodiment of the presentinvention. FIGS. 9A to 9C are cross-sectional views taken along III-IIIof FIG. 8 illustrating a fabricating sequence of an array substrateaccording to the first embodiment of the present invention. In FIG. 9A,a gate line 125 and a gate electrode 132 are formed on the substrate 111by depositing conductive metal such as aluminum (Al), aluminum alloys,molybdenum (Mo), copper (Cu), tungsten (W) and chromium (Cr), forexample, and patterning it. If the gate electrode 132 and the gate line125 are formed of aluminum (Al), an additional conductive metal layerfor protecting the gate electrode 132 and the gate line 125 may beformed. A gate insulating layer 141 is formed on the substrate 111 andon the gate electrode 132 by depositing or coating organic insulatingmaterial or inorganic insulating material. The organic insulatingmaterial for the gate insulating layer 141 is selected from a groupincluding benzocyclobutene (BCB) and acrylic resin. The inorganicinsulating material for the gate insulating layer 141 is selected from agroup including silicon oxide (SiO₂) and silicon nitride (SiN_(X)). Asemi-conductor layer 134 is formed on the gate insulating layer 141 bydepositing an amorphous silicon layer and impure amorphous silicon layeron the gate insulating layer 141 and patterning it. A data line 127crossing the gate line 125, a source electrode 133 connected to the dataline 127 and a drain electrode 135 being spaced apart from the sourceelectrode 133 are formed by depositing conductive metal material on thewhole area of the substrate 111 and patterning it. Though it is notshown in the figure, an align key is formed on the corner of thesubstrate 111 during the gate line 125 of FIG. 8 forming process or thedata line 127 forming process.

In FIG. 9B, a first passivation layer 143 is formed on the substrate bydepositing an inorganic insulating material such as silicon oxide (SiO₂)or silicon nitride (SiN_(X)) and then patterning it to form a draincontact hole 145 exposing a part of the drain electrode 135. The firstpassivation layer 143 is formed thin. As a result, it can be formed thinon the align key allowing an uneven shape of the align key be remained.

In FIG. 9C, a reflective electrode 147 that contacts the drain electrode135 through the drain contact hole 145 is formed on the firstpassivation layer 143 by depositing and patterning a conductive metalmaterial such as aluminum (Al) or aluminum alloys that has a lowelectric resistance and high reflexibility. At this time, a detection ofthe align key can be performed well during the depositing and etchingprocess for the reflective electrode 147. Accordingly, a process errorcaused by an alignment error of the mask and the substrate does notoccur during the reflective electrode forming process. A secondpassivation layer 149 is formed on the substrate 111 by depositingorganic insulating material.

If silicon nitride (SiN_(X)) is formed beneath the reflective electrode147, the electrical conduction property of the liquid crystal panel canbe improved and contact property between the reflective electrode 147and the first passivation layer 143 can be improved, which results in animprovement of electric properties of a liquid crystal panel.

A second embodiment of the present invention will be describedhereinafter with reference to FIG. 10 and FIGS. 11A to 11E. FIG. 10 is aplan view illustrating a partial array substrate having an invertedstagger type thin film transistor for a transflective liquid crystaldisplay device according to the second embodiment of the presentinvention. FIGS. 11A to 11E are cross-sectional views taken along lineV-V of FIG. 10 illustrating a fabricating sequence of an array substrateaccording to the second embodiment of the present invention. In FIG.11A, because a thin film transistor forming process is the same as thatof the first embodiment, i.e., a reflective liquid crystal displaydevice, it will not be described in detail herein.

As shown in FIG. 11A, a gate electrode 132, a source electrode 133, adrain electrode 135, an active layer 134 and a data line 127 are formedon a substrate 111 in sequence. Though it is not shown in the Figures,an align key for accurate aligning of the mask and the substrate isformed on the corner of the substrate simultaneously with the gate lineor the data line forming process. The shape of the align key is uneven.Accordingly, a detector aligns the mask and the substrate by irradiatinglight onto the uneven surface of the align key and sensing the lightreflected from the surface of the align key.

In FIG. 11B, a first passivation layer 149 is formed on the substrate111 and on the thin film transistor “T” by depositing inorganicinsulating material such as silicon nitride (SiN_(X)), for example, onthe substrate 111. Because the first passivation layer 149 is formedthin on the substrate 111 compared with organic insulating material suchas benzocyclobutene (BCB), for example, the uneven shape of the alignkey may remain. A first drain contact hole 150 a for exposing a part ofthe drain electrode 135 is formed by patterning the first passivationlayer 149.

In FIG. 11C, a reflector 153 that includes a transmission hole 151 inthe pixel region is formed by depositing and patterning a metal such asaluminum (Al) and aluminum alloys, for example, on the first passivationlayer 149. At this time, a detection of the align key can be achievedwell during the depositing and etching process for the reflector 153.Accordingly, a process error caused by an alignment error of the maskand the substrate is not occurred during the reflective electrodeforming process.

In FIG. 11D, a second passivation layer 154 is formed on the substrate111 by depositing transparent organic insulating material such asbenzocyclobutene (BCB) and acrylic resin. A second drain contact hole150 b that exposes a part of the drain electrode 135 is formed byetching the second passivation layer 154 corresponding to the firstdrain contact hole 150 a of FIG. 11C and an etching hole 155 is formedby etching the second passivation layer 154 corresponding to thetransmission hole 151. At this time, the first passivation layer 149 maybe etched simultaneously with the second passivation layer 154.

In FIG. 11E, a transparent pixel electrode 157 that contacts the drainelectrode 135 through the drain contact hole is formed by depositing andpatterning transparent conductive material such as indium tin oxide(ITO) or indium zinc oxide (IZO), for example, on the second passivationlayer 154.

Whereas the drain electrode is exposed by etching the first passivationlayer 149 and the second passivation layer 154 respectively in adifferent process as in FIG. 11B and FIG. 11D, the drain contact holecan be formed by etching the first passivation layer 149 and the secondpassivation layer 154, simultaneously in a single process.

A third embodiment of the present invention will be describedhereinafter with reference to FIG. 12 and FIGS. 13A to 13F. FIG. 12 is aplan view illustrating a partial array substrate having a coplanar typepolysilicon thin film transistor for a transflective liquid crystaldisplay device according to the third embodiment of the presentinvention. FIGS. 13A to 13F are cross-sectional views taken along linesIV-IV, V-V and VI-VI of FIG. 12 illustrating a fabricating sequence ofan array substrate according to the third embodiment of the presentinvention.

In FIG. 13A, a first insulating layer 162, i.e., a buffer layer, isformed on the transparent insulating substrate 160 by depositinginorganic insulating material such as silicon oxide (SiO₂) or siliconnitride (SiN_(X)). The buffer layer 162 is optional. A polysilicon layer164 is formed by depositing amorphous silicon (a-Si: H) on the bufferlayer 162 and crystallizing the amorphous silicon.

In FIG. 13B, a semi-conductor layer 166 is formed by patterning thepolysilicon layer 164. The semi-conductor layer 166 has a semi-conductorlayer expanded portion 167 corresponding to a pixel region “P” of FIG.12. The semi-conductor layer 166 can be divided into a first activeregion “A” that serves as an active channel and a second active region“B” that is ion doped. A second insulating layer 168, i.e., a gateinsulating layer, is formed on the substrate 160 and on thesemi-conductor layer 166 by depositing inorganic insulating materialsuch as silicon oxide (SiO₂) or silicon nitride (SiN_(X)), for example,on the substrate 160. A gate electrode 170 over the first active region“A”, a gate line 171 connected to the gate electrode 170 and a gate pad174 connected to one end of the gate line 171 are formed by depositingand patterning conductive metal material on the second insulating layer168. A storage line 172 is simultaneously formed parallel to the gateline 171 and the storage line 171 has a storage line expanded portion173.

In FIG. 13C, a third insulating layer 176, i.e., interlayer insulatinglayer, is formed by depositing insulating material on the whole area ofthe substrate 160. A first contact hole 178 a and a second contact hole178 b, which expose the second active region “B” of the semi-conductorlayer 167 are formed. A source electrode 180 and a drain electrode 182,which contact the exposed second active region “B” are formed bydepositing and patterning conductive metal such as aluminum (Al),aluminum alloys, chromium (Cr), tungsten (W), molybdenum (Mo) andniobium (Nb), for example, on the third insulating layer 176. A dataline 184, which is connected to the source electrode 180 and verticallyextended form the source electrode 180 is formed on the third insulatinglayer 176. A data pad is formed at one end of the data line 184. Thedata line 184 defines a pixel region “P” by crossing the gate line 171.A polysilicon thin film transistor is formed through the aboveprocesses.

In FIG. 13D, a fourth insulating layer 188 is formed by depositinginorganic insulating material such as silicon oxide (SiO₂) or siliconnitride (SiN_(X)), for example, on the substrate 160. The thin filmtransistor then undergoes a hydrogenation process. The hydrogenationprocess is for removing defects occurred on the surface of the activelayer 166 and the fourth insulating layer 188 may be formed of siliconnitride (SiN_(X)) that includes hydrogen. A fifth insulating layer 190is formed by depositing transparent organic insulating material such asbenzocyclobutene (BCB) or acrylic resin, for example, on the fourthinsulating layer 188. A sixth insulating layer 200, i.e., a barrierlayer, is formed by depositing inorganic insulating material such assilicon oxide (SiO₂) or silicon nitride (SiN_(X)), for example, on thefifth insulating layer 190.

In FIG. 13E, a reflector 202 is formed in the pixel region “P” bydepositing and patterning conductive metal material such as aluminum(Al) or aluminum alloys, for example, on the barrier layer 200. As shownin the figure, the reflector 202 is formed over the storage lineexpanded portion 173. However, the reflector 202 may be formed over thethin film transistor and extended to cover the gate line 171 and thedata line 184. The reflector and the storage line expansion portion 173constitute a reflection portion “E” of FIG. 12 in the pixel region “P”of FIG. 12 and the remaining portion of the pixel region “P” of FIG. 12is a transmission portion “F” of FIG. 12. Accordingly, an area ratiobetween the reflection portion and the transmission portion can becontrolled by varying the reflector 202 and the storage line expansionportion 173. A seventh insulating layer 205 is formed by depositinginorganic insulating material such as silicon oxide (SiO₂) or siliconnitride (SiN_(X)), for example, on the substrate 130 and on thereflector 202. A drain contact hole 192 that exposes a part of the drainelectrode 182 is formed by etching the fourth insulating layer 188, thefifth insulating layer 190, the sixth insulating layer 200, i.e., thebarrier layer and the seventh insulating layer 205 over the drainelectrode 182. A gate pad contact hole 194 that exposes the gate pad 174is formed by etching laminated insulating layers from the thirdinsulating layer 176 to the seventh insulating layer 205 over the gatepad 174. A data pad contact hole 196 that exposes the data pad is formedby etching laminated layers from the fourth insulating layer 188 to theseventh insulating layer 205 over the data pad 186.

An under-cut and an inversed taper, which occurs in the wall of theplurality of the contact holes can be prevented by equalizing an etchingspeed of the transparent organic insulating layers with the etchingspeed of the plurality of inorganic insulating layers. The equalizing ofthe etching speeds of the laminated layers is performed by adding about65˜80% of oxygen gas to etching gas (SF₆, CF₄).

In FIG. 13F, a pixel electrode 198 contacts the exposed drain electrode182 through the drain contact hole 192. A gate pad terminal 201 contactsthe gate pad 174 through the gate pad contact hole 194. A data padterminal 204 contacts the data pad 186 through the data pad contact hole196. The pixel electrode 198, gate pad terminal 201 and data padterminal 204 are formed by depositing and patterning transparentconductive metal material such as indium tin oxide (ITO) or indium zincoxide (IZO), for example, on the seventh insulating layer 205 and in therespective contact hoels 192, 194 and 196.

The transflective liquid crystal display device of the present inventionhaving a high aperture ratio can be manufactured through themanufacturing process described above.

As described above, an array substrate for reflective and transflectiveliquid crystal display devices includes a reflective electrode thatavoids being formed directly on an organic insulating layer such asbenzocyclobutene (BCB) by exchanging a forming order of the organicinsulating layer and an inorganic insulating layer such as siliconnitride (SiN_(X)) or by introducing a barrier layer between the organicinsulating layer and the reflective electrode. Accordingly, the arraysubstrate with reflective electrode formed in this matter avoids theproblems of the conventional art discussed above.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. An array substrate for a reflective liquid crystal display device,the substrate comprising: a gate line and a data line defining a pixelregion by crossing each other; a switching element at a crossing portionof the gate line and the data line; a first passivation layer coveringthe switching element and the data line, the first passivation layerbeing formed of an inorganic insulating material; a reflective electrodeon the first passivation layer, the reflective electrode being connectedto the switching element; and a second passivation layer on thereflective electrode, the second passivation layer being formed of anorganic insulating material.
 2. The device according to claim 1, whereinthe reflective electrode includes conductive metal material such asaluminum (Al) or aluminum alloys.
 3. The device according to claim 1,wherein the switching element is a thin film transistor including a gateelectrode, a source electrode, a drain electrode and an active layer. 4.The device according to claim 1, wherein the first passivation layerincludes silicon nitride (SiN_(X)).
 5. The device according to claim 1,wherein the second passivation layer is an organic insulating materialincluding benzocyclobutene (BCB) or an acrylic resin.
 6. A manufacturingmethod of an array substrate for a reflective liquid crystal displaydevice, the method comprising the steps of: forming a gate line and adata line such that the gate line and data line define a pixel region bycrossing each other; forming a switching element at a crossing portionof the gate line and the data line; forming a first passivation layercovering the switching element and the data line, the first passivationlayer being formed of an inorganic insulating material; forming areflective electrode on the first passivation layer, the reflectiveelectrode being connected to the switching element; and forming a secondpassivation layer on the reflective electrode, the second passivationlayer being formed of an organic insulating material.
 7. The methodaccording to claim 6, wherein the reflective electrode is formed ofconductive metal material including aluminum (Al) or an aluminum alloys.8. The method according to claim 6, wherein the switching element is athin film transistor including a gate electrode, a source electrode, adrain electrode and an active layer.
 9. The method according to claim 6,wherein the first passivation layer is formed of silicon nitride(SiN_(X)).
 10. The method according to claim 6, wherein the secondpassivation layer is formed of an organic insulating material includingbenzocyclobutene (BCB) or an acrylic resin.
 11. An array substrate for atransflective liquid crystal display device, the substrate comprising; athin film transistor including an active layer, a gate electrode andsource and drain electrodes, formed sequentially on a substrate; a gateline including connected to the gate electrode; a gate pad at a firstend of the gate line; a storage line parallel to the gate line andspaced apart from the gate line; a data line defining a pixel region bycrossing the gate line, the data line being connected to the sourceelectrode; a data pad at one end of the data line; an organic insulatinglayer over the thin film transistor and the data line; a barrier layeron the organic insulating layer, the barrier layer being formed of aninorganic insulating material; a reflector on the barrier layer; aninorganic insulating layer between the reflector and the pixelelectrode; and a transparent pixel electrode on the inorganic insulatinglayer, the pixel electrode contacting the drain electrode.
 12. Thesubstrate according to claim 11, further comprising: an insulating layerbeneath the organic insulating layer for performing a hydrogenationprocess of the thin film transistor.
 13. The substrate according toclaim 11, further comprising: a buffer layer beneath the active layer,the buffer layer including an inorganic insulating material such assilicon oxide (SiO₂) or silicon nitride (SiN_(X)).
 14. The substrateaccording to claim 11, wherein the active layer is formed ofpolysilicon.
 15. The substrate according to claim 11, wherein thestorage line and gate line are formed of a same material and on a samelayer.
 16. The substrate according to claim 11, wherein the reflector isformed of a conductive metal material including aluminum (Al) or analuminum alloys.
 17. The substrate according to claim 11, wherein thepixel electrode is formed of a transparent conductive material includingindium tin oxide (ITO) or indium zinc oxide (IZO).
 18. The substrateaccording to claim 11, wherein the reflector extends to the data lineand covers the thin film transistor.
 19. The substrate according toclaim 11, wherein the reflector is partially overlapped with the gateline or the data line.
 20. The substrate according to claim 11, whereinthe reflector covers the thin film transistor.
 21. The substrateaccording to claim 11, wherein the barrier layer is formed usinginorganic insulating material including silicon oxide (SiO₂) or siliconnitride (SiN_(X)), for example.
 22. A method of forming an arraysubstrate for a transflective liquid crystal display device, the methodcomprising the steps of: forming a thin film transistor including asubstrate and sequentially forming an active layer, a first insulatinglayer, a gate electrode, a second insulating layer and source and drainelectrodes on the substrate; forming a gate line and a storage line, thestorage line being formed parallel to the gate line and being spacedapart from the gate line; forming a gate pad at a first end of the gateline; forming a data line defining a pixel region by crossing the gateline, the data line being connected to the source electrode; forming adata pad at a first end of the data line; forming a third insulatinglayer over the thin film transistor and the data line, the thirdinsulating layer being formed of transparent organic insulatingmaterial; forming a fourth insulating layer on the third insulatinglayer, the fourth insulating layer being a barrier layer and beingformed of inorganic insulating material; forming a reflector on thebarrier layer; forming a drain contact hole over the drain electrode bydepositing and patterning a fifth insulating layer on the reflector;forming an inorganic insulating layer between the reflector and thepixel electrode; and forming a transparent pixel electrode on theinorganic insulating layer, the pixel electrode contacting the drainelectrode.
 23. The method according to claim 22, further comprising:forming an insulating layer beneath the organic insulating layer toperform a hydrogenation process of the thin film transistor.
 24. Themethod according to claim 22, further comprising: forming a buffer layerbeneath the active layer using an inorganic insulating materialincluding silicon oxide (SiO₂) or silicon nitride (SiN_(X)).
 25. Themethod according to claim 22, wherein the active layer is formed ofpolysilicon.
 26. The method according to claim 22, wherein the storageline and gate line are formed with a same material and on a same layer.27. The method according to claim 22, wherein the reflector is formed ofa conductive metal material including aluminum (Al) or an aluminumalloy.
 28. The method according to claim 22, wherein the pixel electrodeis formed of transparent conductive material including indium tin oxide(ITO) or indium zinc oxide (IZO).
 29. The method according to claim 22,wherein the reflector is extended to the data line and covers the thinfilm transistor.
 30. The method according to claim 22, wherein thereflector is partially overlapped with the gate line or the data line.31. The method according to claim 22, wherein the reflector covers thethin film transistor.
 32. The method according to claim 22, wherein thebarrier layer is formed using an inorganic insulating material includingsilicon oxide (SiO₂) or silicon nitride (SiN_(X)).
 33. The methodaccording to claim 22, wherein the drain contact hole is formed byetching the third insulating layer, the fourth insulating layer and thefifth insulating layer simultaneously with an etching gas includingabout 65-80% of oxygen gas.